Thermal circuit breaker



a F. sMAFzT THERMAL CIRCUIT BREAKER June 14, 319270 Filed July 31, 19232 Sheeis-Sheec F. S MART June THERMAL C IRCUI T BREAKER Filed July 51,

Patented June 14, 1927.

UNITED STATES 1,632,420 PATENT OFFICE.

JOSEPH F. SMART, OF NEW BRITAIN, CONNECTICUT ASSIGNOR TO LANDEfis, FBARYd:

CLARK, OF NEW BRITAIN, CQNNECTICUT, A CORPORATION OF CONNECTICUT.

THERMAL CIRCUIT BREAKER.

Application filed J'uly 31, 1923. Serial No. 654,890.

heated utensil as it approaches a dangerous degree of heat, the aim ofthe invention being to provide a device of this sort having features ofnovelty andv advantage.

More particularly, the object of the inven-- tion is to provide acircuit breaker of this sort which 15 very sensitlve 1n operation inthat it will break the circuit with surety when the temperature of theutensil, wit which it is associated, rises to within very small limitsof the temperature at which the device is adjusted; which may be reset avery short time after the device has. been automatically operated; whichmay be adjusted with nicety to operate at any predetermined temperatureabove which it-is dangerous to heat the utensil; which is compact andeconomical in construction and which is housed within the utensil so itdoes not detract from the appearance of the utensil and so that itcannot be injured nor readily tampered with; and which may bemanipulated 2 or set in a ready manner without removing any parts ordisassembling the utensil.

Other ob'ects' of the invention will be part obviousan 'in part pointedout more particularly hereinafter.

In the accompanying drawings:

Figure 1 is a top plan view of an electrically heated utensil, forinstance a sad iron, in which is embodied one form of my invention, thecover of the iron being removed for purposes of clearness, and the partsof my circuit breaker being illustrated in latched or on position;

Fig. 2 is a side view of the sad iron looking in the direction of thearrow 2 of Figure 1 and with the casing of the iron in centrallongitudinal section;

Fig. 3 is a view similar to Figure 1 but with the parts of the circuitbreaker shown in unlatched or of! sition;

Fig. 4 is an enlarge sectional view, taken substantially on line 4-4 ofFig. 3; and

Fig. 5 is a fragmentary view, in top plan, of a portion of the handle ofthe sad iron with the setting lever of the circuit breaker positionedtherebeneath.

In the drawings, I have shown my device applied to a sad iron, but it isto be understood that my invention is applicable for use generally onelectircally heated utensils, the present disclosure being by way ofillustration only and, therefore, it is not to be taken as restrictiveof my conception.

Referring to the drawmgs in detail, a denotes the sole plate of theiron; I), a solid vmetal top plate; and c, an electrical heating elementof any suitable construction posi-. late and the top tioned between thesole plate and insulated there rom. .ie is a sheet metal cover or casingwhich encloses the top "plate, the heating unit, and the thermo-,'static device or cut-out of the present invention; and k is a handlesuitably held in plaice pn the casing as by means of screws or Thethermostatic device of the resent invention includes a circuit closeraving, in the present instance, a pivoted plate 10 resiliently carryinga circuit closing element 11 adapted to en age, and thereby close thecircuit between, t e contact members 12 and 12' interposed in one of theleads of the heating unit 0; a thermostat 9 arranged to hold the circuitcloser in circuit closing position until the utensil reaches apredetermined heat, resulting in the thermostat being flexed anddisengaged from the circuit closer whereupon the latter will be throwninto off position breaking the circuit through the electrical heatingunit; and the setting device or lever 13 sitioned on the outside of thecasing and a apted to be manually operated to place the circuit-closerin on position after the iron has cooled suficiently to permit thethermostat to hold the circuit closer in this position.

The thermostat 9 comprises a pair of bimetal bars 14 and 15 each securedat one end to a U-shaped sheet metal plate 16 pivoted for rotarymovement on the top plate by means of a screw 17. Fixed to one end ofone of the bi-metal bars, in the present position, as hereinafterdescribed more in etail. The thermostat .9 is normally urged in adirection togenga'gethe roller'18 with the, circuit closer, by means ofa s ring 20 ositioned about 'thescrew 17. The other i-metal bar 15 isarranged to flex in a di-,

which stop is, by preference, adjustable so 1s, of course, understoodthat each of the bimetal bars is composed of two strips of metal havingdifferent co-efiicients of expansion and welded or otherwise securedtogether. In the present illustrative disclosure, the strips of metalhaving a lesser coeflicient of expansion are positioned on the outsideof those strips which have a great co-eflicient of expansion. p

The latch plate 10 is pivotally on the top plate by a screw 23 and isnormally urged by a spring 24 in a counterclockwise direction, referringto Fig. 1, that is in a direction in which the circuit closing element11 is moved away from the contacts 12, 12. The latch plate 10 isprovided with a depending tongue 26 to which is secured, by means of aspring 27, the circuit closing element or contact blade 11. The contactblade is, of course, suitably insulated from the latch plate. The latchplate is further provided with a shoulder or stop 30 against which theanti-friction roller 19 is adapted to engage and thereby hold thecircuit closer in latched or on position.

Fixed to the to plate b, as-by means of one of \the nuts is a supportingbracket 34 on the up-turned portion of which the contacts 12 and 12 aresecured, these members, however, being insulated from the supportingbracket. The contact member '12 is electrically connected to oneiend ofthe heating element or unit 0 by a stri 35. The opposite end of theheating unit is directly connected to a terminal post by a strip 37, andthe contact member 12 is connected by a strip 38 to the other terminalpost 36. It will thus be seen that the current will normally flowthrough one of the terminal posts, strip 37, the electrical heating unit0, the strip 35, contact 12, circuit closing element 11, contact 12,strip 38, and the other terminal 0st 36 connected with the lastmentioned strip.

For the purpose of re-setting or re-latching the circuit breaker, thereis provided on the top of the cover e and beneath the strap or bail h ofthe handle a setting lever 13 connected to the cover. e by means of apin 41 fixed to the cover and engaging in an elongated slot 42 in thelever. The lever 13 has an upwardly extending projection or lip 43 bymeans of which the lever may be thrown, and this rojection. or lipnormally lies close to the side of the handle strap 72., where it is outof the way. It will be seen, particularly from Fig. 2, that the casingis provided with beads 44 upon which the nandle bail rests, and there isthus provided between the handle bail and the casing a mountedspace forthe lever 13. Carried by the latch plate 10 and extending through anarcuate elongated opening 45 in the casing e is a pin or stud 46 to theupper end of which the lever 13 is pivotally connected. The lever 13 hasa thickened boss '47 for'receiving this pin, and the strap h is offsetupwardly as at 48 to accommodate this boss.

The operation of the device is briefly as follows. Assuming that theparts of the circuit breaker are in latched or on position, as shown inFig.1, so that the current is flowing through the heating unit; when thetemperature of the utensil gradually rises, the bi-metal bars 14 and 15are flexed or bowed in opposite directions. Since the shoulder 30 of thelatch plate is urged against the anti-friction roller 19 carried by thebar 14, this bar bends at its intermediate portion towards the center ofthe iron, causing the plate 16, to which the parts are secured, to turnslightly in a clockwise direction. Owing to this turning movement of theplate 16 and the flexure of the bar 15, the freeend of the latter, whenthe predetermined temperature is reached, at which the device is set tooperate, engages the adjustable stop 21 whereupon the antifrictionroller 19 will'be disengaged from the latch plate permitting the latter,under the influence of the spring 24, to rotate in a direction towithdraw the circuit closing-element 11 out of engagement with thecontacts 12 and 12, thereby breaking the circuit through the heatingunit. The parts will now assume the position shown in Fig. 3. It will beobserved that the two thermostatic bars, when heated, are flexed inopposite directions and the arrangement is such that the flexure ormovement of both of these bars is-combined or aggregated to release thecircuit breaker. The thermostatic bars are placed side by side so thatthey take but a relatively small amount of space. Thus, there isprovided an arrangement which, while extremely compact, has athermostatic device of sufiicient capacity and size to operatepositively and sensitively at any desired predetermined temperature atwhich the device may be set to throw the current ofi. Owing to theprovision of the anti-friction roller 19, friction between thethermostat and the latch plate is reduced to a minimum. The roller willreadily ride out of engagement with the latch plate when the thermostathas been flexed to a predetermined extent, and sticking of the parts ispractically eliminated.

One of the advantages of the arrangement illustrated and described isthat the circuit breaker may be re-set into circuit closing position avery short time after the breaker is operated to break the circuit; thatis to say, the operator of the iron need allow but a very little timefor the iron to cool slightly before he can again throw the current ontothe heating unit, this being due to the fact that the thermostatic barssimultaneously flex back towards each other upon being.

.When the lever is in final position, the lip 43 lies closely to thebail so that it is out of the way and causes no annoyance orinconvenience. It will be understood that when the lever is thus pushedto re-set the device, the lever is fulcrul'ned against the pin 41' andmoves, through the pin 46, the latch plate to t-he'position shown inFig.1. All of the parts of the circuit breaker are enclosed within thecasing and are thus protected and do not in any way mar the appearanceof the iron. The lever 13 is so positioned that it is practically out ofsight.

I claim as my invention:

1. A thermal circuit breaker including a circuit closer, andthermostatic means normally holding said closer in circuit closingposition, said means including a plurality of thermostats, one of whichis arranged to normally hold said closer in circuit closing posicuitclosing position, an

static member arranged to move said pivoted tion and the other of whichis arranged to move said first thermostat, said thermostats being soarranged that their responses to temperature changes are combined toefl'ect release of the closer.

2. A thermal circuit breaker including a circuit closer, a pivotedmember, a thermostatic member carried by said pivoted member andnormally holdin said closer in cir-- a second thermomember andthermostatic member carried thereby.

3. A thermal circuit breaker including a circuit closer, a pivotedmember, and thermostatic means normally holding said circuit closer incircuit closing position, said means comprising a pjluralit ofthermostatic elements carried y sai pivoted member and so arranged thattheir responses to temperature changes are combined to effect release ofsaid closer. I

4. A thermal circuit breaker including a circuit closer, thermostaticmeans normally holding said closer in circuit closing position, saidmeans comprising a plurai thermostatic elements movable in oppositedirections upon temperature changes and so asranged that their responsesto tem erature iiihan esare combined to effect re ease of said c oser,and adjustable means for regulating the operation of said thermostaticmeans.

5. A thermalcircuit b ty of.

' Tker including a circuit closer, means normally urging the same intoopen position, a pivoted member, and a pair of thermostatic bars carriedby said pivoted member and arranged to normally hold said closer incircuit closing position. i

7 A thermal circuit breaker including a circuit closer, an abutment, anda pair of thermostatic bars placed side by side and adapted to flex inopposite directions, one of said bars being engageable with said circuitcloser to hold the same in circuit closing position, and the other ofsaid bars being operatively connectedto and movable with said first barand adapted to engage said abutment and thereupon move said first bar.

thermal circuit breaker including acircult closer, means normally urgingthe 8. A thermal circuit breaker including a engageable with saidcircuit closer an when flexed under heat changes, adapted to move theother or second of said bars towards said abutment, and said second bar.

being adapted to en age said abutment and therebyrmove said rst bar outof engagement with said closer.

10. A thermal circuit breaker including a pair of contacts, a circuitcloser having a latch plate pivoted at one side and a circuitclosingelement resiliently connected to said plate and adapted to engage saidcontacts, a spring associated with said plate for normally urging thesame ina direction to withdraw said element from said contact-s,

said plate'havin at the side opposite the pivotal point, a s oulder, athermostatic bar flexible 1n the plane of said plate and adapted toengage said shoulder, and means for moving said circuit closer intocircuit closing position. i t

11. A thermal circuit breaker for electrically heated utensils,including a supporting plate, a cover housing said sup orting plate, apair of contacts, a circuit 0 oser having a latch plate pivoted to saidsup porting plate and located beneath said cover, said closer further.includin a circuit closing element carried by said latch plate,thermostatic means carried by said supporting plate and arranged to holdsaid closerin circuit closing position, and pivoted means for re-settingsaid latch plate in circuit closing position connected to said latchplate and extending through an arcuate slot in said cover.

12. A thermal circuit breaker for electrically heated utensils,including a supporting plate, a cover housing said plate, a pair ofcontacts, a circuit closer having a latch plate pivoted to saidsupporting late and located geneath said cover, said 0 o'ser furtherinclu ing a circuit closing element carried by said latch plate,thermostatic means carried by said supporting plate and arranged to holdsaid closer in circuit clos- -ing position, a lever resting on theoutside of said cover, a stud pivotally connecting said lever to saidlatch late, and a pin connecting said lever to said-cover, said coverhaving an arcuate slot to accommodate said stud and said lever having aslot to accommodate said pin.

13. A thermal circuit breaker for electrically heated utensils,including a supporting plate, a cover therefor, a strap connected tosaid cover, a circuit closer beneath said cover, thermostatic means fornormally holding said closer in circuit closing position, and a leverpositioned between said'strap and cover. and operatively connected tosaid circuit closer for re-setting the latter in circuit closingposition.

14. A thermal circuit breaker for elccv ing lip adapted to lie closelyagainst said strap when the lever is in its normal posi tion.

JOSEPH F. SMART.

